The evolution of the human brain depended on many apparently trivial mechanisms. For example, what if cells had not developed the ability to manufacture myelin? Unmyelinated axons must be very large if they are to transmit action potentials rapidly. How big would the human brain have to be if oligodendrocytes did not produce myelin? Could the human brain as we know it have evolved without myelin?
In what ways is the human brain different from other species (non-primate and non-human primate)? What are the features of a highly evolved brain? Why is a convoluted brain better than a smooth one?
There has been a lot of interesting debate about men's brains being larger than women's brains. Does size matter? Is brain size related to more complex behaviors/intelligence? If so, why? If not, why not?